Introduction

A simple alternative to OpenGL polygon tesselation callback. You can focus on file triangle.h that contain the class to evaluate convexity of polygon and tesselate the polygon. No extra points are inserted. You can work only with planar polygon also in 3D.

Every suggestion in order to speed up the class and create better tesselation ('better' triangles) is appreciated.

It appeared as though the Delauney method only worked for polygons that were contained within the convex hull of the set of polygons. It appears as the method shown here works on concave polygons as well.

A more little explanation about my article. In order to tesselate the polygon i use this tecnique:First compute the normal of polygon (i use the newell method see Graphic Gems..)For each sequence of three vertex ( i, j, k ) in the polygon compute the vector area (alias normal of triangle). If the normal go in the opposite direction of polygon normal the triangle is 'concave' and go ahead.If the area il 0.0 the point j is alligned from i to k and eliminated from the list of vertex.If the normal of triangle is in the same direction of polygon normal the triangle is convex. In the last case check if any other point is inside the triangle (the IsPointInside function). This function test if the point is on solid angle ik ^ jk. if this is true compute distance of intersection k->point to line ij and test distance. If all is good emit triangle, remove vertex j from list and go to the next triplet....The reason for wich i posted this article is that i don't find this tecnique in any book or article and ave a doubt about the mathematical basic of my algoritm In other words is true that it work in any case ? (my experience ask yes but is very far from a theorem...)The Delauney algortim work fine but is 'computational' more expensive than my algortim (using my Delauney implementation) for this reason i try this way. At the end my apologize fro my poor english but my sincerly idea is to contribute to codeproject and suggest a way to resolv a problem that i found. Thanks pepito.

That is, why don't you put some explanation of the problem itself, the solution utilized by your code, the potential use of the code and some code examples of how to use it in another application etc. ?

Sorry, and my apologize, but my english is very poor.!!!! This is a basic class to use in alternative to tools like gluTesselate. The glu function is much flexible but in the (frequent) case in wich you ave a simple polygon this class let you to take a more control. For instance:dont insert new points in the polygon (and if you attach vertex property like color or vertex texture coordinate dont request any interpolation of this parameters)dont use expensive time functions like square root etc. is fast like gluTesselate (try it)work in 3D

Anonymous wrote:Perhaps because his English isn't too hot?Who made you the article Gestapo around here?

You must understand that it takes more than just good code to make a good article. An explanation of how and why is essential.

Even if English isn't your first language, there's no reason an author shouldn't write it first in his or her own native language and then ask for assistance (via the Collaboration/Testing forum or even the Lounge) in translating it into English before posting.

Of course, these days you can also do some limited translation via the web, which may be enough.

Remember that there's no need to worry about English in an article being perfect - CPians are pretty understanding of language barriers.

What is wrong with you people? The guy has put together an interesting piece of code that people like me and possibly many others appreciate. Whilst I agree it is possible to get far more out of an article when it is properly written up, if someone submitting an article doesn't want to, or feels it would take excessive time to translate into a language that is not their own, then it is up to them. I wish people would stop being so critical of other people's efforts. If you don't like the article don't read it. If you have a criticism to make then at least be constructive. If you are that bothered Andy then why not offer to translate an article yourself. And as for George...

People contibuting code should be encouraged. It takes 5 minutes to write a criticism and boost your ego, it takes a lot more effort to write a decent peice of code.